Modulation of multi-drug resistant gene expression in human breast cancer cells by dietary gossypol

537

Acquired multi-drug resistance during treatment is a major cause for chemotherapy failure. It has been shown that P-glycoprotein, a transmembrane protein, encoded by multidrug- resistance (MDR1) gene, pumps drugs out of the cell thus reducing drug accumulation in the tumor cells. Our SuperArray results demonstrated that PPAR alpha was up-regulated after treating MCF-7 cells with (-) gossypol (3μM ) or (-) gossypol enriched cottonseed oil (GPCSO). 0.1% GPCSO delivers approximately 0.16μM (-)GP. The purpose of this study was 1) to evaluate the effect of different chemotherapy agents Tamoxifen, ICI 182 780 and Adriamycin alone, or combined with (-) GPCSO on MCF-7 Adr cells and primary human breast cancer epithelial cell proliferation and 2) to examine if (-)GPCSO alone, or combined with different chemotherapy agents can modulate both MDR1 and PPAR alpha gene expression in a multidrug resistant cell line and in primary cultured human breast cancer cells. A cell proliferation assay was conducted by using CellTiter 96® Non-radioacitve method. MDR1 and PPAR alpha mRNA expression were analyzed by Taqman real time PCR after 24 hour treatment, The results indicated that 0.01 to 1μM of tamoxifen, ICI 182 780 and Adriamycin have no inhibitory effect on MCF- 7 Adr cells and primary human breast cancer epithelial cells growth. Meanwhile, 0.05% (-)GPCSO can significantly inhibit both MCF-7 Adr cells and breast cancer epithelial cells proliferation in the presence or absence of 0.1 mM tamoxifen, ICI 182 780 or Adriamycin. Compared to 0.1μM tamoxifen, ICI 182 780 and Adriamycin alone, the addition of 0.05% (-)GPCSO can inhibit primary breast cancer epithelial cells growth at about 94%, 90%, and 71% respectively. (-)GPCSO increased PPAR alpha mRNA expression in MCF-7 cells in a dose dependent manner(0.1 -1μM). 0.1 and 1μM Adriamycin has no effect on MDR1 mRNA expression in MCF-7 Adr cells, but 0.1μM Adriamycin combined with 0.025, 0.05, and 0.1% (-)GPCSO, reduced MDR1 mRNA expression about 14.7%, 17.6% and 35% respectively. Our results show that (-)GPCSO might be a potent chemopreventive agent in the diet that can be widely used in breast cancer prevention or in combination with chemotherapy for multidrug resistant breast cancer patients. Our results also indicated that PPAR alpha is a potential biomarker for multi-drug resistant research. (supported by NIH Grants CA 94718 and CA 95915 and DOD Breast Cancer Research Program Grants DAMD 8140,0319 and 9341)